Dispensing device

ABSTRACT

A dispensing device (50) for dispensing fluent material, e.g. a lubricant, over a prolonged period of time comprising a cylinder (2), a piston (6) and/or extendable membrane separating the cylinder into a fluent material containing first chamber (69) and a second electrolyte containing chamber (9), a sacrificial first electrode (61), a gas-releasing second electrode (63) connected to the first electrode, the electrodes not being in contact with the electrolyte prior to activation of the device, and means for adjusting the surface area of the second electrode which will be exposed for contact with the electrolyte on activation of the device. A method of lubricating a machine bearing is also disclosed.

This invention relates to a dispensing device of the kind comprising acylinder, dispensing means (e.g. a piston device, an extendable membraneor a combination of a piston and an extendable membrane) movable withinthe cylinder and separating the cylinder into a first chamber containingfluent material and having a discharge outlet and a second chambercontaining an electrolyte, a sacrificial first electrode, agas-releasing second electrode electrically connected to the firstelectrode, the first and second electrodes being of differentgavanically active materials, e.g. metallic or carbon, and which, onactivation of the device, are brought into contact with the electrolyteso as to electrochemically generate gas within, and increase thepressure within, said second chamber thereby causing the dispensingmeans to move within the cylinder to discharge said fluent materialthrough the discharge outlet. The invention primarily relates tolubricant dispensing devices which are mounted on machinery and dispenselubricant into lubricating channels of bearings of the machinery at asteady rate over a prolonged period of time, e.g. from one to twelvemonths. However the invention may also find application in the automaticdispensing over a period of time of other types of fluent material, suchas other liquids, pastes, gels or even powder material. The inventionalso relates to a method of dispensing fluent material at a controlledrate over a period of time.

A known dispensing device of the kind referred to for dispensinglubricant is described in GB-A-1401535. In this known device the firstand second electrodes are formed as a bi-polar galvanic element which isinitially contained in a third chamber separated from the second chamberby a common frangible wall. A separate screw-threaded activating memberis inserted into the third chamber and, on being turned, pushes thegalvanic element against the common frangible wall fracturing the latterand pushing the galvanic element into the electrolyte contained in thesecond chamber. The second chamber has flexible, elastomeric walls and apiston device and, as gas is electrochemically generated, the secondchamber expands moving the piston device towards the discharge outlet.Such known dispensing devices are well proven in practice and the meansfor activating the device to initiate and preserve the steadyelectrochemical generation of gas has been both accurately predictableand reliable. However there is a disadvantage with such known dispensingdevices in that the rate of discharge of lubricant from the dischargeoutlet is determined by the construction of the galvanic element and inparticular is dependent on the exposed surface area of the gas-releasingelectrode which contacts the electrolyte. These galvanic elements aresealed into the dispensing devices during manufacture and cannot bechanged or replaced after manufacture. It is thus necessary formanufacturers to make, and for distributors and purchasers to stock, arange of devices which are able to discharge lubricant at a steady rateover different periods of time, e.g. from one to twelve months.

In order to overcome the above-identified disadvantage, it has beenproposed in WO-A-8909907 to modify the design of dispensing device shownin GB-A-1401535 by incorporating the galvanic element in a cavity withinthe screw-threaded activating member which is sealed by a destructibleor soluble foil. In use, the screw-threaded member is screwed into thethird chamber causing both the destructible or soluble foil which sealsthe cavity and the common frangible wall to break so that the galvanicelement is released into the electrolyte contained in the secondchamber. In practice the destructible or soluble foil has been dispensedwith and the activating-member has mechanical claws which grip thegalvanic element until the activating member is screwed home. In boththese devices a common electrolyte containing body part can be used withany one of a plurality of different screw-threaded members incorporatingdifferent galvanic elements. Although these arrangements dispense withthe need to make and stock a complete range of complete dispensingdevices, it is still necessary for a manufacturer to make, anddistributors and users to stock, a range of different screw-threadedmembers incorporating different galvanic elements. Since the galvanicelement is a relatively costly part of a dispensing device, the economicbenefits to be obtained by these arrangements are limited.

Another known lubricant dispensing device which is available on themarket is disclosed in EP-A-0278138. This known device employsconventional torch batteries for passing current through an electrolyteto generate gas within an expansible chamber. As the latter expands withthe generation of gas, a piston moves and expels lubricant from adischarge outlet of the device. A complicated electrical system ofswitches and resistors is provided for setting, and if necessaryadjusting, the rates of gas generation and lubricant dispensing. Withsuch a design it is not necessary to provide an entire range ofdifferent dispensing devices. However, this known dispensing device hasthe disadvantages that it is relatively expensive to produce, because ofits complicated electrical equipment, and could prove unreliable in usebecause of the inherent fallibility of electrical circuit assembliesincluding the batteries when used over extended periods.

Various other lubricant dispensing devices have been proposed whichincorporate electrical means for generating gas, for switching thereaction on or off and/or for altering the lubricant discharge ratewhilst in use. Examples of such devices are shown in WO-A-8800657,WO-A-8804751 and WO-A-8908800. However all these dispensing devices havethe disadvantages of the relatively high cost and inherent fallibilityof complicated electrical apparatus when used over extended periods.

The present invention seeks to overcome the disadvantages discussedabove by providing a dispensing device in which gas generation isachieved by the well proven method of bringing galvanically dissimilarmetals or other materials into contact with an electrolyte and in whichmeans are provided for selecting, typically pre-selecting, the rate ofdischarge of fluent material, typically a lubricant, from the device.

According to one aspect of the present invention a dispensing device ofthe kind referred to is characterised in that the dispensing devicefurther comprises adjusting means for adjusting the amount of surfacearea of the second electrode exposed for contact with said electrolyteon activation of the device.

A dispensing device according to the invention employs a reliable, wellproven method of generating gas in which the rate of discharge of fluentmaterial through the discharge outlet can be selected as required,typically prior to activation of the device, by adjusting the amount ofthe surface area of the second electrode exposed for contact with theelectrolyte. It is therefore not necessary for manufacturers to produce,or for distributors and users to stock, a range of dispensing deviceshaving different operating or lubricating periods. Instead a single typeof dispensing device is provided which can be adjusted by the user tooperate for a desired period of time to suit a particular requirement.

The dispensing means typically comprise a piston device but could,alternatively, comprise an expansible membrane or a combination of apiston device and an expansible membrane.

Conveniently the adjusting means comprises an adjustment member movably,preferably turnably, mounted in an end wall of the cylinder remote fromthe discharge outlet and in that the first and second electrodes arecarried by an electrode unit having relatively movable., preferablyrelatively turnable relative to a turning axis, first and second housingparts movable to expose different amounts of the surface area of thesecond electrode, the electrode unit being positioned, prior toactivation of the device, in an adjustment position in which electrolytein the second chamber is prevented from contacting the first or secondelectrode and in which the adjustment member is movable, preferablyturnable, to relatively move, preferably turn, said housing parts toadjust the amount of the surface area of the second electrode exposedfor contact with the electrolyte on subsequent activation of thedispensing device. Suitably said housing parts are relatively turnableabout a turning axis and define a sealed cavity with an opening thereincoaxial with the turning axis, the second electrode being movablymounted in the sealed cavity and projecting through the opening, theamount that the second electrode projects through said opening beingadjustable by turning of said adjustment member.

As an alternative construction the first and second housing parts of theelectrode unit may cover the second electrode, the first housing parthaving a plurality of openings therein and the second housing parthaving at least one opening therein, the turning of the adjustmentmember causing the first and second housing parts to turn relative toeach other to place different opening of the first and second housingparts in registry with each other to expose different parts of thesurface area of the second electrode. Typically the housing partsinclude concentric cylindrical parts or coaxial flat parts in sliding,turnable relationship with each other.

In an alternative construction incorporating an electrode unit, theelectrode unit, prior to activation of the device, is detachably fixedin, so as to block, a tubular passage opening into the second chamberand the adjusting means comprises a plug carrying a covering member, theplug being insertable into the tubular passage to plug the latter, toposition the covering member so as to partially cover an exposed surfaceof the second electrode and to dispense the electrode into the secondchamber. Suitably the tubular passage and plug are provided with matingscrew-threads, the plug being screwed into and out of the tubularpassage. In the electrode unit, the second electrode is preferably ofelongate, cylindrical form positioned coaxially with the tubular passagewhen the electrode unit is fixed in the tubular passage prior toactivation of the device. In this case the covering member comprises asleeve which is pushed on to the elongate electrode as the plug isinserted into, e.g. screwed into, the tubular passage. By providing anumber of plugs each carrying a differently sized sleeve, the amount ofsurface area of the second electrode remaining exposed after a sleevehas been pushed onto it can be pre-selected. In use the plug isinserted, e.g. screwed, downwardly into the tubular passage so that thesleeve is initially pushed onto the upwardly projecting secondelectrode. In the final stage of plug insertion, the electrode unit ispushed into the second chamber. The plug blocks the tubular passage inits fully inserted position to prevent the electrolyte from escapingfrom the second chamber. A sealing ring is suitably provided for sealingbetween the tubular passage and the plug when the latter is in its fullyinserted position. Although a number of plugs need to be provided foreach dispensing device, these plugs are made from inexpensive plasticsmouldings and are relatively inexpensive to make. The relativelyexpensive galvanic element is contained in the main unit of thedispensing device.

In an alternative embodiment the second chamber may be divided into afirst sub-chamber containing the electrolyte and a second sub-chamberadjacent the piston device, the first and second sub-chambers beingseparated by a dividing wall which during use enables the passagetherethrough of gas (e.g. it is gas permeable) but prevents the passagetherethrough of liquid electrolyte (i.e. it is electrolyte impermeable).In this case the dividing wall is conveniently rigid or semi-rigid.Typically the dividing wall is substantially gas-impermeable but isprovided with a number of spaced apart gas-permeable portions. However,alternatively, the dividing wall may be completely gas-permeable. Inthis embodiment the discharge rate of the dispensing device may bere-adjusted or re-set after activation of the device.

In another embodiment, in which the electrodes comprise an electrodeunit, the second electrode may be of elongate form projecting into thesecond chamber and the first electrode may be fixed to a free endportion of the second electrode which projects into the second chamber.Turning of the adjusting means adjusts the surface area of the secondelectrode exposed to contact with the electrolyte. As with thepreviously described embodiment, the discharge rate may be re-set afterinitial activation of the device. The second electrode may include acylindrical portion slidable within electrolyte sealing means, e.g. anO-ring or the like. Alternatively, instead of the first electrode beingfixed to the second electrode, the first electrode may be fixed in anend wall of the device and the second electrode mounted for movementrelative thereto on turning of the mechanical means to adjust the amountby which the second electrode projects into the second chamber. In thiscase the adjusting means may comprise a screw-threaded portion of thesecond electrode rotatable to vary the amount that the second electrodeprojects into the second chamber. Suitably the first electrode is in theform of an annular disc through which the second electrode movablyprojects and a cover member is mounted on the free end of the secondelectrode which covers the first electrode when the second electrode isin a limit position.

In a further embodiment, the second electrode may be movably mounted ina wall of the device at an angle to the axis of the cylinder. In thiscase the adjusting means may include a bevel gear and toothed track onthe circumference of a circle centred on the cylinder axis, the teeth ofsaid track engaging with the bevel gear for effecting movement of thesecond electrode. Again the rate of gas discharge can be re-adjusted orre-set after initial activation of the dispensing device.

The first and second electrodes may be made of any suitable galvanicallyactive metallic or other materials. For example the first electrode maycomprise zinc or aluminium and the second electrode may comprisemolybdenum or stainless steel. Carbon is one example of a non-metallic,galvanically active material.

According to another aspect of the present invention there is provided amethod of lubricating a machine bearing as claimed in the ensuing claim25.

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying drawings in which:

FIG. 1 is a schematic sectional view through a first embodiment of adispensing device according to the present invention prior to insertionin a tubular passage of an actuating plug to initiate activation of thedevice,

FIG. 2 is a view of the device shown in FIG. 1 with the actuating plugpartially inserted into the tubular passage,

FIG. 3 is a view of the device shown in FIG. 1 with the actuating plugfully inserted into the tubular passage so that an electrode unit,previously retained in the tubular passage, is ejected into anelectrolyte-containing chamber of the dispensing device,

FIG. 4 is an enlarged schematic sectional view of the upper end of thedevice shown in FIG. 1,

FIG. 5 is a schematic sectional view through a second embodiment of adispensing device according to the present invention,

FIG. 6 is a schematic sectional view through a third embodiment of adispensing device according to the invention,

FIG. 7 is a sectional view through an upper part of a fourth embodimentof a dispensing device according to the invention,

FIG. 8 is a sectional view on an enlarged scale of an electrode unit foruse with the dispensing device shown in FIG. 7,

FIGS. 9 and 10 are views from above on enlarged scales of housing partsof the electrode unit shown in FIG. 12,

FIG. 11 is a schematic sectional view of a fifth embodiment of adispensing device according to the invention,

FIG. 12 is a schematic view of part of a sixth embodiment of adispensing device according to the invention,

FIG. 13A is a schematic sectional view of part of a seventh embodimentof a dispensing device according to the invention,

FIG. 13B is an end view of the dispensing device shown in FIG. 13A, and

FIG. 14 is a schematic sectional view of an eighth embodiment of adispensing device according to the invention.

FIG. 1 shows a dispensing device 1 according to the invention forautomatically dispensing lubricant over an adjustable period of time.The device 1 comprises a transparent or translucent plastics casingcomprising an integral cylinder 2 and end wall 3 and a cup-shaped endpart 4 fixed to the cylinder 2 and having an externally screw-threadeddischarge outlet 5 sealed by an end cap (not shown). A piston device 6is positioned within the cylinder 2 and comprises a plastics support 6aand a flexible rubber diaphragm 6b which seals against the inner surfaceof the cylinder 2. The piston device 6 divides the cylinder into a loweror forward first chamber 8 containing a lubricant to be dispensed and anupper or rearward second chamber 9 containing a liquid electrolyte.

An internally screw-threaded tubular passage 11 is formed coaxially inthe end wall 3 and an electrode unit 12 is positioned, in a snap-fitconnection, at the lower end of the tubular passage 11 to block thelatter and prevent the electrolyte contained in the second chamber 9from passing through the tubular passage 11.

The electrode unit 12 (see FIG. 4) comprises a flat electrode, in theform of an annular zinc disc 13, arranged at the bottom of a cylindricalmolybdenum rod 14 constituting a second electrode. The annular disc 13is positioned within a non-electrically conducting plastics container 15having connection means, e.g. a snap-fit or screw-threaded connection,into which a lower portion of the rod 14 is engaged. An electricallyconductive but galvanically unreactive annular disc 16, e.g. a tinnedmetallic washer, is positioned between the bottom of the disc 13 and thebottom of the opening in the container 15 in which the disc 13 isreceived. This disc 16 contacts both the molybdenum rod 14 and the zincdisc 13 so that the rod 14 is electrically connected to the disc 13.

The end wall 3 is provided with an electrolyte filling and ventingopening 20 closed by a screw member 21.

The device 1 further includes a plug, generally designated 23,comprising a one-piece plastics moulding 24, a plastics sleeve 25 closedat its upper (as viewed in the Figures) end and open at its lower end,an open-ended tubular sleeve member 26 and arcuate shroud parts 27circumferentially positioned between the sleeve 25 and sleeve member 26.The plastics moulding 24 comprises a cylindrical body part 33 with ahandle 28 extending upwardly from one end and, extending downwardly fromits other end, a cylindrical central portion 29 and an externallyscrew-threaded outer annular portion 30 spaced from the central portion29 to provide an annular gap 31 in which the tubular sleeve member 26 isslidably received. The upper end of the sleeve member 26 has an annularbead on its outer surface which is received in an annular recess at thelower or outer end of the inner surface of the annular portion 30 toretain the sleeve member 26 in an extended end position in a snap fit.The plastics sleeve 25 is supported at its lower end by the arcuateshroud parts 27 positioned coaxially between the lower end of the sleeve25 and the lower end of the sleeve member 26. As can be more clearlyseen in FIG. 4, the inner or upper ends of the shroud parts 27 areprevented from axial movement by interengaging with the end of thecentral portion 29. The outer or lower ends of these shroud parts 27 areurged resiliently outwards but are contained by the surrounding sleevemember 26.

The sleeve 25 has one or more calibrated openings 35 in its cylindricalsurface. A sealing ring 36 is positioned at the upper end of the annularsurface of the cylindrical body part 33.

In use, the plug 23 is positioned at the entrance to the tubular passage11 and the sleeve 25 is pushed down, in an interference push fit, ontothe rod 14 so that the lower end of the sleeve member 26 engages, in theextended end position of the latter, the lower annular end of thetubular passage 11. The plug 23 is then screwed into the tubular passage11, until the shroud parts 27 contact the disc 13 (see FIG. 2) and thesleeve member 26 moves relatively upwardly within the annular gap 31from its extended position. Continued screwing of the plug into thetubular passage 11 causes the central portion 29 to urge the shroudparts 27 against the electrode disc 13 until the electrode unit 12 ispushed out of its snap-fit engagement within the tubular passage 11. Asthe sleeve member 26 moves into a retracted position within the annulargap 31, the shroud parts 27 lose their radially outer support and springapart at their lower ends so as to no longer support the sleeve 25. Theelectrode unit 12 with the sleeve 25 fitted to the rod 14 fall into thesecond chamber 9. The plug 23 is finally fully screwed into the tubularpassage 11 (see FIG. 3) so that the sealing ring 36 makes sealingcontact between an annular seating surface 40 of the tubular passage 11and the cylindrical body part 33.

The contact of the electrodes of the electrode unit 12 with theelectrolyte contained in the second chamber 9 causes gas to beelectrochemically generated. As gas is generated in the second chamber9, the piston device 6 moves downwardly dispensing the lubricantcontained in the first chamber 8 through the outlet 5. The rate of gasgeneration is determined by the area of the rod 14 exposed for contactwith the electrolyte which is determined by the size of the calibratedopenings 35. In practice a number of colour coded plugs 23 are providedeach carrying a sleeve with differently calibrated openings 35 dependingon the length of time that it is required for the dispenser to operate,e.g. 3 months, 6 months or 1 year. These plugs 23 are made of mouldedplastics components which are relatively inexpensive to manufacture.Only one electrode unit 12 containing the relatively expensive galvanicelements is required for each dispensing device.

Since the walls of the casing of the device 1 are transparent ortranslucent, the position of the piston device 6 can be viewed from theoutside. If required the wall of the casing may be calibrated with ascale 49 or the like to facilitate reading how far the piston device hastravelled and how much lubricant remains to be dispensed.

It will be appreciated that any suitable electrolyte may be provided inthe second chamber 9. Typically, however, the electrolyte comprisescitric acid possibly with the addition of a detergent or wetting agentand a freezing point lowering agent. The two electrodes of the electrodeunit must be of different galvanically active metallic or othermaterials. Although the preferred material for the disc 13 is zinc andfor the rod 14 is molybdenum, other materials may be used. For example,the electrode disc 13 may comprise aluminium and the electrode rod 14may comprise stainless steel.

FIG. 5 illustrates another embodiment of a dispensing device, generallydesignated 50, according to the invention. Where possible similar partsof the devices 1 and 50 have been identified by similar referencenumerals and will not be described in detail.

The device 50 has an end wall 3 with a tubular passage 11a leading to anelectrolyte-containing second chamber 9. An internally screw-threadedsleeve 51 having a flange 52 at its lower end is rotatably mountedwithin the passage 11a. An O-ring seal 53 is located between the flange52 and the lower surface of a radially inwardly extending annular wallportion 54 at the upper end of the passage 11a and a circlip 55, fixedto the sleeve 51, abuts against an upper surface of the annular portion54. A rotatable knob 56 is mounted on the upper end of the sleeve 51 anda screw-threaded ejecting member 57 is screwed into the sleeve 51. Theknob 56 has splines 56a cooperating with splines on the outer surface ofthe sleeve 51 to enable the knob to move axially but not rotatably, withrespect to the sleeve 51. The enlarged head of the ejecting member 57ensures that the knob 56 cannot slide upwardly off the sleeve 51 whilstthe ejecting member is in screw-threaded engagement with the sleeve. Thelower end of the passage 11a is closed by a closure member 58 in asnap-fit connection.

A chamber or cavity 59 is defined in the tubular passage 11a between theclosure member 58 and the sleeve 51. In this cavity is received anelectrode unit 60 comprising a flat, metallic electrode 61, e.g. in theform of a zinc disc, electrically connected by an electricallyconductive but galvanically unreactive bolt 62 to a cylindricalelectrode 63 of a different metal, e.g. molybdenum. The cylindricalelectrode 63 is fixed within a cylindrical plastics cap 64 having acylindrical wall 64a, which closely covers the cylindrical surface ofthe electrode 63, and an end wall portion 64b which covers the upper endsurface of the cylindrical electrode 63. The end wall portion 64b has anupwardly projecting part which projects into the sleeve 51 and is keyedto the latter, e.g. by cooperating flutes, so as to be movable axially,but not turnably, relative thereto. A further cylindrical cap 65 has acylindrical wall 65a closely surrounding the cylindrical wall 64a and anend wall 65b which covers the lower end surface of the electrode 63 andwhich is turnably mounted on the bolt 62. The cap 65 is keyed to thetubular passage 11a, e.g. by means of cooperating flutes, to preventrotational movement, but to allow axial movement, of the cap 65 relativeto the tubular passage. The sleeve 51, knob 56, ejecting member 57,cylindrical walls 64a and 65a, electrodes 61 and 63 and bolt 62 allshare a common longitudinal axis 69.

The cylindrical wall 64a is provided with a plurality of angularlyspaced apart, differently sized openings 66 exposing different areas ofthe electrode 63. The cylindrical wall 65a is provided with a single,large opening 67, typically having a size similar to the largest opening66.

In use, prior to activation of the device 50, the rate of gas productionin the activated device 50 is pre-set by turning the knob 56 so as toturn the sleeve 51 within the tubular passage 11a. Since the sleeve 51is keyed to the cap 64, the latter turns with the sleeve 51. However,the cap 65 is prevented from turning since it is keyed to the tubularpassage 11a. Thus the cylindrical wall 64a is turned within thesurrounding, coaxial cylindrical wall 65a so that different ones of theopenings 66 can be placed in registry with the opening 67. In this waydifferent parts of the cylindrical surface of the electrode 63, each ofdifferent surface area, are exposed through the opening 67, all othersurfaces of the electrode 63 being covered by the caps 64 and 65. Thereis an interference fit between the cylindrical walls 64a and 64b toprevent the ingress of electrolyte therebetween when the electrode unitis subsequently immersed in the electrolyte whilst allowing relativeturning between the caps 64 and 65.

After the caps 64 and 65 have been turned relative to each other into apre-set condition--i.e. for generation of gas at a desired rate so thatthe dispensing device 50 will dispense material, e.g. lubricant such asoil or grease, over a desired period of time--the electrode unit 60 isdispensed into the second chamber 9. This is achieved by screwing theejecting member 57 downwardly so that the electrode unit 60 is pusheddownwardly. As the ejecting member 57 is screwed axiallydownwards,radially outwardly extending longitudinal flutes 56b on theknob 56 cooperate with radially inwardly extending longitudinal flutes3b formed in an opening of the end wall 3 so as to lock the knob 56against rotation thereby preventing alteration of the pre-setting of thecaps 64 and 65. Furthermore, the electrode unit 60 is pushed axiallydownwards against the closure member 58 forcing the latter to becomedetached from the lower end of the tubular passage 11a so that theelectrode unit 60 can fall into the chamber 9. Alternatively, if thedevice 50 is inverted in use, electrolyte from the chamber 9 can flowinto the tubular passage 11a. In either case, the ejecting member 57 hasan O-ring seal 68 which seals with the sleeve 51 to provide aliquid-tight seal.

When the electrode unit 60 is immersed in the electrolyte, gasgeneration commences and the piston device 6 moves downwardly tocommence dispensing of the lubricant. The interference fit between thecylindrical walls 64a and 65a ensures that they remain in their pre-setcondition throughout the electrochemical reaction.

FIG. 6 shows an alternative construction of dispensing device 70 similarto the device 50 but provided with a different electrode unit 71. Wherepossible similar reference numerals have been employed to identify partssimilar to those of the other dispensing devices described herein.

The electrode unit 71 comprises a disc-shape electrode 72 fixed within aplastics covering member 73 having a plurality of differently sizedopenings 78 therein. The covering member 73 is rotatably mounted withina plastics cylindrical member 74 having an end wall 75 with a largeopening 76 therein. An electrically conducting, galvanically inactivepin 77 connects electrode 72 to another electrode 83. The member 73 iskeyed against rotation, e.g. by longitudinally and radially inwardlyextending flutes thereon cooperating with longitudinally and radiallyoutwardly extending flutes of the sleeve 51 and the member 74 is keyedagainst rotation, e.g. by longitudinally and radially outwardlyextending flutes on the member 74 cooperating with longitudinally andradially inwardly extending flutes of the tubular passage 11a.

In order to pre-set the electrode unit 71, the knob 56 is turned so asto turn the covering member 73 relative to the cylindrical member 74 toselectively place different ones of the openings 78 in registry with theopening 76. As with the device 50, the electrode unit 71 is ejected intothe second chamber 9 by screwing the ejecting member 57 downwardly intothe sleeve 51 so as to lock the control knob in position and todisconnect the closure member 58 from the tubular passage 11a.

The two dispensing devices 50 and 70 provide accurate and reliablepre-settings of the length of time of operation of the devices. At thesame time the methods of ejecting the electrode units into the secondchamber is reliable. The piston 6 for each device 50 and 70, comprises arigid moulded plastics having a pair of axially spaced apart O-ringseals 80 and 81 which seal against the inside of the cylinder 2.

FIGS. 7 to 10 show another embodiment of a dispensing device 85according to the invention. Where possible similar reference numeralshave been used to identify parts similar to those of the dispensingdevice 50. The lower part of the cylinder 2 and end part 4 are not shownbut are similar to the dispensing devices shown in FIGS. 5 and 6.

The dispensing device 85 has an electrode unit 86 (shown fully in FIG. 8but only partly in chain lines in FIG. 7) partly within a cavity definedby the tubular passage 11a. The electrode unit 86 comprises a lowerhousing part 87 having a bottom wall 88, and a cylindrical wall 89having a pair of upstanding posts 90 and 91. A further pair of posts 92and 93 extend upwardly from the bottom wall 88. The posts 90 to 93 arediametrically aligned as can be seen in FIG. 9, although the outer posts90 and 91 project upwardly further than the inner posts 92 and 93. Anupper housing part 94 is rotatably connected to the lower housing part87 and comprises a cylindrical wall 96 and, at its upper end, a centralboss 95 with a hole 100 (see FIG. 10) therethrough which is joined tothe wall 96 by four equally spaced apart radial arms 101. The wall 96 isinternally screw-threaded and is positioned concentrically, radiallyinside, the wall 89. The wall 96 has upper and lower circumferentialprojections 97a and 97b in snap-fit connection with upper and lowercircumferential recesses 98a and 98b in the wall 89.

A first electrode in the form of an electrode disc 102 with an axialcentral opening is fixed within the upper housing part 94 with theradial arms 101 positioned above it and the central boss 95 positionedwithin its central opening. A sealing plate 104 of a conductive butgalvanically inactive material, e.g. tinned metal, with a centralopening is positioned beneath, and in contact with, the electrode disc102; the plate 104, bottom wall 88 and cylindrical walls 89 and 96together defining a sealed cavity 99.

Within the cavity 99 is positioned a non-conductive, e.g. plastics,carrier 105 having an external screw-threaded surface in screw-threadedengagement with the internally screw-threaded surface of the wall 96.The carrier 105 has two diametrically arranged holes 106 therein throughwhich extend the posts 92 and 93. A second electrode in the form of acylindrical electrode pin 107 is carried coaxially on the carrier 105and projects upwardly through the central hole in the plate 104 and thehole 100 in the boss 95. The electrode pin 107 has a liquid tight,sealing fit within the hole 100. On rotation of the upper housing part94 relative to the lower housing part 87 about turning axis T, thescrew-threaded engagement of the carrier 105 with the wall 96 causes thecarrier 105 to move axially within the cavity 99. Thus the distance thatthe electrode pin 107 projects upwardly through the hole 100 can beadjusted. Electrical contact between the first and second electrodes isensured by means of a metallic helical spring 110 which surrounds theelectrode pin 107 and extends between the plate 104 and a conductivecirclip 111 fixed to a bottom part of electrode pin 107. Alternatively,to reduce the number of electrical connections, the plate 104, circlip111 and spring 110 could be replaced by electrically conductive,galvanically neutral, springy electrical contacts (not shown buttypically two would be provided) connecting the electrode disc 102 tothe electrode pin 107. In this case the electrode disc 102 would behoused in a compartment closed at the bottom except for openings throughwhich parts of the spring contacts project. The spring contacts would belocated at the bottom of this compartment except for the projectingparts which would extend through the bottom of the compartment andresiliently contact the cylindrical surface of the electrode pin 107.

The electrode unit 86 is detachably fixed within the tubular passage 11aby a circumferential rib 112 at the top of the lower housing part 87which makes a snap-fit connection with a co-operating circumferentialrecess 113 at the bottom of, on the inner surface of, the tubularpassage 11a. To prevent turning of the housing part 87 relative thetubular passage 11a, the upstanding posts 90 and 91 are received indownwardly open recesses 114 and 115 in the tubular passage 11a.

The upper housing part 94 has upwardly open recesses 120 and 121 (seeFIG. 10) in which are received downwardly extending legs 108 and 109 ofthe sleeve 51 to cause the upper housing part 94 to turn relative to thelower housing part on turning of the sleeve 51. The sleeve 51 is turneditself by turning the actuating knob 56c which is keyed to the sleeve 51by cooperating flutes (not shown). Thus by turning the knob 56c, thesleeve 51 is turned which turns the upper housing part 94 relative tothe lower housing part 87 causing the carrier 105 to move axially withinthe cavity thereby changing the amount by which the electrode pin 107projects through the hole 100. A peripheral flange 56b of the knob 56cand the adjacent peripheral part of the end wall 3 suitably havemarkings to indicate the setting of the device, i.e. the length of aprolonged period of time that the device will continue to dispenselubricant after activation of the device.

The dispensing device 85 is activated by turning a screw-threadedejecting member 57a to eject the electrode unit 86 into the secondchamber 9. The member 57a is externally screw-threaded on its centralcore and is in screw-threaded engagement with an internallyscrew-threaded bore of the sleeve 51. The lower end of the member 57ahas a blind axial hole 57b therein to accommodate the electrode pin 107when the latter projects through the hole 100, the length of the hole57b being sufficient to accommodate the pin 107 when the latter projectsits maximum distance. On screwing the member 57a downwardly, the lowerend of the member 57a pushes downwardly against a plastics thrust plate130 which transfers a downward force to the upper housing part 87. Thiscauses the electrode unit 86 to become detached from its connection withthe tubular passage 11a so that it is ejected into the second chamber 9.

Another embodiment of dispensing device according to the invention isshown in FIG. 11 and is identified by the reference 140. Where possible,the same reference numerals have been used to identify similar parts ofpreviously described devices.

The dispensing device 140 has an end wall 141 in which is mounted anelectrode assembly generally designated 142. The electrode assemblycomprises a sleeve 143 of tinned brass or copper having an internallythreaded upper (as viewed in FIG. 11) portion 144 and a non-threadedflanged lower portion 145. An annular zinc disc 150 constituting a firstelectrode, is arranged at the lower end of the sleeve 143, the latterprojecting through the central opening of the annular disc 150. As canbe seen in FIG. 11, the upper portion 144 of the sleeve is receivedwithin an intermediate portion 148 of a through bore 146 formed in theend wall and having a counterbored lower portion 149 and a grooved upperportion 147. The annular disc 150 is secured in the lower bore portion149. The electrode assembly 142 further comprises a molybdenum rod 151forming a second electrode and having a cylindrical lower portion 152and an externally threaded upper or head portion 153 screw-threadedlyengaged with the threaded upper portion 144 of the sleeve 143. The rod152 is thus electrically connected to the disc 150 through the sleeve143. A plastics cover 154 is attached to the lower end (as viewed inFIG. 11) of the rod 151. The bore 146 is closed by a cap 156 having ashort splined shaft 156b received in interengaging relationship with thegrooved upper bore portion 147. The spline and groove interengagementallows the axial removal and insertion of the cap 156 from the bore 146but prevents turning of the cap relative to the bore. The cap 156 has aradially outwardly directed pointer 156a on its upper surface and aseries of numbers from "0" to "12" are arranged circumferentially on ascale 157 on the upper surface of the end wall 141 radially outwardly ofthe cap 156. An O-ring seal 158 is retained within an inwardly openingannular groove of the lower portion 145 for sealing against the lowerrod portion 152 and preventing the passage of either electrolyte or gasfrom the sub-chamber 12 between the sleeve 143 and rod 151.

In use of the dispensing device 140, the cap 156 is removed from itsclosure position in the bore 146 and a screwdriver or the like isinserted through the bore portion 147 and inside the sleeve 143 torotate the head portion 153. Initially the rod 151 is in an uppermostposition (as viewed in FIG. 11) with the cover 154 covering the annulardisc 150. In this respect it will be noted that the cover hasfrusto-conical walls which are intended to seal against correspondingfrusto-conical walls of the end wall 141 surrounding the disc 150. Inthe uppermost position of the rod 151, the disc 150 and rod 151 are notexposed to contact with the electrolyte contained in the sub-chamber 12.On rotation of the head portion 153 in a clockwise direction the rod 151moves downwardly. As the rod moves downwardly, the cover 154 revealsboth the disc 150, and an increasing length of the lower portion 152, tocontact with the electrolyte contained in the sub-chamber 12 thusinitiating the electrochemical generation of gas. Conveniently, from theuppermost position of the rod 151, a single clockwise rotation of thehead portion 153 will provide for 12-month operation of the device, twoclockwise rotations of the head portion will double the rate of gasgeneration and thus halve the operation period so that the deviceoperates for 6 months. It follows that 4-month operation will requirethree clockwise revolutions, 3-month operation will require fourclockwise revolutions and 2-month operation will require six clockwiserevolutions. For 1-month operation, the rod 151 will be in its lowermostposition reached by twelve full rotations of the head portion 153. Ifappropriate gearing (not shown) were provided, it is possible that thedevice could be designed so that there was a direct relationship betweenthe number of revolutions turned and the length of operation of thedevice. Once the desired operational time period has been set by theuser, the cap 156 is pushed back into the bore 146 but oriented so thatthe pointer 156a is directed towards the figure on the scale 157identifying the number of months of operation of the dispensing device.Typically the rod 151 will have a length of travel of about 10 mmbetween its upper and lower positions and the exposed portion of the rod151 will have a diameter of about 2 mm. The diameter dimension for therod is very critical for particular combinations of electrolytes andelectrodes and can be calculated in theory and verified by experimentfor any particular electrolyte/electrode combination. The cup-shapedmember 11 is typically made of gas-impermeable andelectrolyte-impermeable material. In this case, plugs 159 ofgas-permeable and electrolyte-impermeable material may be fixed in thewalls of the member 11. As shown in FIG. 11, one such plug 159 is shownin the member 11 with the portion of the member 11 beneath the plug 159having through openings 160 formed therein. Normally more than one plug159 is provided, but the plug 159 shown would operate to allow gasgenerated in the sub-chamber 12 to pass to the sub-chamber 13 if thedevice 140 were used in an inverted condition. In that case, since thesub-chamber 12 is never completely filled with electrolyte, a gas spacewould be provided above the upper surface level of electrolyte containedin the inverted dispensing device and gas in this gas space would beable to pass through the plug 159 into the sub-chamber 13.

A modified version of the dispensing device 140 is schematically shownin FIG. 12 and is identified by the reference number 162. The maindifferences between the dispensing devices 140 and 162 are in thecup-shaped member, identified by reference numeral 174 in FIG. 12,defining in part the sub-chamber 12 and the electrode assembly 163. Onlythese items will be described in detail below.

The dispensing device 162 has an electrode assembly generally designatedby the reference 163. The electrode assembly 163 comprises an annularzinc disc 164 constituting a first electrode arranged at the bottom of amolybdenum rod 165 constituting a second electrode. The annular disc 164is positioned within a non-electrically conducting plastics container166 having a screw-threaded bore into which a lower portion 168 of therod 165 is screw-threadedly engaged. An electrically conductive butgalvanically inactive annular disc 170, e.g. a tinned metallic washer,is positioned between the bottom of the disc 164 and the bottom of theopening in the container 166 in which the disc 164 is received. Thisdisc 170 contacts both the molybdenum rod 165 and the zinc disc 164 sothat the rod 165 is electrically connected to the disc 164. Althoughmeans are not shown for effecting upward and downward movement of theelectrode assembly 163, any suitable mechanical means may be provided.The mechanical arrangement may involve rotating inclined cammingsurfaces, gearing arrangements operable on turning or rotation of acontrol knob or a simple screw-threaded arrangement such as is shown inFIG. 2. Whatever mechanical means is employed, the rod 165 is moveablebetween an upper position in which the disc 164 is positioned against adownwardly facing annular surface 172 of the end wall 3 and a lowerposition (as shown in FIG. 12). Typically the length of rod 165 exposedin the lower position of the electrode assembly is about 10 mm and thislength of rod would suitably be used for lubricant dispensing over aperiod of one month. A shorter length of rod 165 would be exposed forlonger periods of time for lubricant dispensing. Since the rod 165 iscylindrical in form, there is a substantially linear relationshipbetween the length of rod 165 exposed to contact with the electrolyteand the rate of gas generation. To prevent or defer erosion of the disc164 where it is joined to the rod 65, a plastics annular disc 167 ispositioned in a coaxial recess formed in the upper surface of the disc164 and positioned against the rod 165. Alternatively, the disc 167 maybe replaced by an annular sleeve (not shown) extending the full heightof the disc 164 between the disc 164 and rod 165 .

The cup-shaped electrolyte containing member 174 is provided with agas-permeable, electrolyte-impermeable lower plug 160 positionedco-axially of the casing of the dispensing device 162. In addition tothe plug 160, a plurality, e.g. three or more, further plugs 175 (onlyone of which is shown in FIG. 12) are positioned around the upperperiphery of the cup-shaped member 174. Conveniently these plugs 175 areequally angularly spaced apart and lie in a common plane perpendicularto the axis of the dispensing device.

In use, the chamber 12, defined by the member 174 and the end wall 3, isnot fully filled with electrolyte. At least one of the plugs 160 and 175is intended to be positioned above the upper level of the electrolytefor any orientation that the dispensing device 162 can be in when in its"in use" position on a machine. Thus, for example, in the orientation ofFIG. 12, all the plugs 175 would normally be positioned above the upperlevel of the electrolyte. If the device were inverted through 180°, theplug 160 would be positioned above the level of the electrolyte. If in ahorizontal disposition, one, or at least part of one, of the plugs 175would be positioned above the level of the electrolyte. Thus, gasgenerated within the sub-chamber 12 is able to pass through at least oneof the plugs 160 and 175 into the chamber 13 for effecting movement ofthe piston device 6 to dispense lubricant through the discharge outlet5.

FIGS. 13A and 13B illustrate a further embodiment of a dispensing deviceaccording to the invention and generally designated by the referencenumeral 180.

In the dispensing device 180, the electrode assembly 142 is similar tothat shown in FIG. 11 and similar parts of the electrode assembly havebeen identified by the same reference numerals. However, it will beappreciated that the electrode assembly is disposed at an angle,typically about 60°, to the axis of the dispensing device 180. In orderto effect movement of the rod 181 into and out of the sub-chamber 12, asplined rod 181 extends rearwardly from the head portion 183 and arearward portion of this splined rod 181 is received within a groovedbore 182 of a tubular member 183 having, at its rearward end, a bevelgear 184. The tubular member 183 is journalled for rotation about theaxis of the rod 11 and the splined rod 181 is moveable axially withinthe grooved bore 182 of the tubular member 183. Rotation of the tubularmember 183 thus causes the rod 181 to be screwed into or out of thesleeve 143. The bevel gear 184 meshes with teeth 186 arranged on thecircumference of a circle on the downwardly facing surface of an endwall 187.

The electrode assembly 142 is mounted on a closure wall 188 which closesthe upper end of a cup-shaped electrolyte containing member 189. Thewall 188 and member 189 form a single unit which is rotatable about theaxis of the dispensing device 180 relative to the casing of the latter.Rotation of this unit causes the bevel gear 184 to mesh with the teeth186 thereby moving the rod 151 into or out of the sub-chamber 12 definedby the member 189 and closure wall 188. This relative rotation iseffected by means of a control knob 190 (see FIG. 13B). The knob 190 hasa central shaft 191 with an enlarged head 192 at its lower end (asviewed in FIG. 13A) received within an upwardly open chamber 193 formedin the closure wall 188. The knob 190 is moveable axially between alower position (shown in FIG. 13A) and an upper position determined bythe relative dimensions of the head 192 and the chamber 193. The openinginto the chamber 193 in the closure wall 188 comprises a grooved bore195. Splines 197 on the shaft 191 are engaged with the grooves of thebore 195 whether the control knob 190 is in its upper or lower positionsso that rotation of the knob will cause the closure wall 188 to rotatewith the knob 190 so that the bevel gear 184 rides around the teeth 186effecting rotary and axial movement of the rod 151. Although not shownin FIG. 13A, the knob 190 has axial splines formed on its cylindricalsurface 198. In the lower position of the knob 190, these splinesinterengage with axial grooves formed in the cylindrical surface 199 ofthe end wall 187 to prevent rotation of the knob 190 relative to the endwall 187. In the upper position of the knob 190, the splines disengagefrom the axial grooves to permit turning of the knob 190 relative to theend wall 187. When in its upper position, the knob 190 is turnable fromits initial "0" position in a clockwise direction and can be positionedagainst any of the numbers "12" through to "1" arranged around theoutside of the end wall 187. It is not possible to turn the knob 190 ina clockwise direction passed the " 1" position. Once set, the controlknob 190 is lowered to engage the splines on the surface 198 with thegrooves in the surface 199. As can be seen in FIG. 13A, an O-ring seal196 is provided between a cylindrical part of the closure wall 188 and aconfronting cylindrical portion of the end wall 187 to prevent theescape of gas from the sub-chamber 13. The lower end of this closurewall cylindrical part has an enlarged tapered head 178 which snap fitsbehind an inwardly directed tapered annular projection 179 formed on theend wall cylindrical portion to retain the end wall connected to theknob 190.

A further embodiment of the invention is schematically shown in FIG. 14and shows a cup-shaped member 211 fixed to end wall 3 which sub-dividesthe second chamber 9 into a first electrolyte containing sub-chamber 212and a second sub-chamber 213 adjacent piston device 6. The member 211 ismade of a rigid or semi-rigid plastics material which is permeable togas but impermeable to the electrolyte and which conveniently comprisesa microporous material, such as microporous polyethylene, polypropyleneor polytetrafluoroethylene.

The end wall 3 supports a sacrifical first electrode 214 and a gasreleasing second electrode 215. Each electrode is slidably mounted andis urged into an upper position, as viewed in FIG. 14, by spring means226 and 227. The electrode 214 is received within a cavity 219 sealed atits front end by a frangible foil 221. A conductive strip 239, e.g. ofcopper, electrically connects the two electrodes 214 and 215.

A control knob 228 is mounted in the end 3 and is actuable to urge theelectrodes 213 and 215 downwardly against the spring urging. The knob228 has camming surfaces schematically identified as 230 and 231 whichcontrol the position of the electrodes on turning of the knob. Initialdownward movement of the electrode 214 causes the foil 221 to fractureso that the electolyte contacts the electrode 214 to initiate theactivation of the device. The rate of dispensing is controlled by theamount of electode 215 which projects into the sub-chamber 212. Anon-conducting plastics portion 225 at the lower end of the electrode215 prevents the electrolyte contacting the electrode 215 until thelatter is advanced by sliding movement from its uppermost position.

It will be appreciated that the dispensing devices described hereinenable the lubricant discharge rate to be adjusted by the user by meansof a simple external mechanical adjustment. This is convenientlyachieved by providing one of a variety of mechanical arrangements on theexterior of the dispensing device and preferably including a turnablecontrol knob actuator. On activation of the device, after adjustment ofthe surface area of the gas-releasing electrode to be exposed to contactwith the electrolyte, the sacrificial and gas-releasing electrodescontact the electrolyte. Once the position of the gas-releasingelectrode has been set or adjusted, the amount of its surface areacontacted by the electrolyte will not change in use of the dispensingdevice except in those embodiments described in which the electrolyte isretained in a gas permeable yet electrolyte impermeable chamber, and theeletrode unit remains fixed to its adjusting mechanism, thus permittingthe user to re-adjust the discharge rate at any desired time afteractivation.

A wall portion of the end part 4 may be weakened, or the joint betweenthe end part 4 and the cylinder 2 may not be strong, so as to fracturein use if a build up of pressure occurs within the lubricant-containingchamber, e.g. as a result of a blocked machine bearing.

I claim:
 1. A dispensing device comprising cylinder means, dispensingmeans movable within the cylinder and separating the cylinder means intoa first chamber containing fluent material and having a discharge outletand a second chamber containing an electrolyte, a galvanic elementcomprising a sacrificial first electrode and a single gas-releasingsecond electrode electrically connected to the first electrode, thefirst and second electrodes being of different galvanically activematerials and which, on activation of the device, are brought intocontact with the electrolyte so as to electrochemically generate gaswithin, and increase the pressure within, said second chamber therebycausing the dispensing means to move within the cylinder means todischarge said fluent material through the discharge outlet, andadjustment means operatively connected to said second electrode forvarying the amount of surface area of the second electrode of thegalvanic element exposed for contact with said electrolyte; whereby therate of gas electrochemically generated is pre-adjusted to control thetime taken for the cylinder means to discharge said fluent materialthrough the discharge outlet.
 2. A dispensing device according to claim1, wherein the adjustment means comprises an adjustment member movablymounted in an end wall of the cylinder remote from the discharge outletand the first and second electrodes are carried by an electrode unithaving relatively movable first and second housing parts movable toexpose different amounts of the surface area of the second electrode,the electrode unit being positioned, prior to activation of the device,in an adjustment position in which said electrolyte in the secondchamber is prevented from contacting the first or second electrodes andin which the adjustment member is movable to relatively move saidhousing parts to adjust the amount of the surface area of the secondelectrode exposed for contact with the electrolyte on subsequentactivation of the dispensing device.
 3. A dispensing device according toclaim 2, wherein the adjustment member is turnably mounted in said endwall and said first and second housing parts of the electrode unit areturnable relative to each other about a turning axis.
 4. A dispensingdevice according to claim 3, wherein said housing parts define a sealedcavity with an opening therein coaxial with said turning axis, thesecond electrode being movably mounted in the sealed cavity andprojecting through the opening, by an amount which is adjustable byturning of said adjustment member.
 5. A dispensing device according toclaim 4, wherein said first and second housing parts have respectivefirst and second cylindrical portions arranged concentrically withrespect to the turning axis with the first cylindrical portion disposedradially inwardly of the second cylindrical portion and wherein thesecond electrode is elongate and is carried on a carrier with itselongate axis coaxial with said turning axis, the carrier having anexternal screw thread in screw-threaded engagement with an internalscrew thread of the first cylindrical portion and having stop meanspreventing turning of the carrier relative to the second housing part,said two screw threads being coaxial with said turning axis, wherebyturning of the adjustment member to turn the first housing part causingthe carrier, with its screw threaded engagement with the firstcylindrical portion, to move axially within said sealed cavity.
 6. Adispensing device according to claim 5, wherein the sealed cavity housesa metal helical spring surrounding the second electrode and ensuringelectrical contact between the first and second electrodes, the springbeing contractible on axial movement of the carrier to project thesecond electrode through the opening.
 7. A dispensing device accordingto claim 3, wherein the first and second housing parts cover the secondelectrode, the first housing part having a plurality of openings thereinand the second housing part having at least one opening therein, theturning of the adjustment member causing the first and second housingparts to turn relative to each other to place different openings of thefirst and second housing parts in registry with each other to exposedifferent parts of the surface area of the second electrode.
 8. Adispensing device according to claim 7, wherein the first housing parthas a tubular first covering portion surrounding the second electrodeand the second housing part has a tubular second covering portionclosely surrounding, and coaxial with, the first covering portion, thefirst and second covering portions including the said openings.
 9. Adispensing device according to claim 7, wherein the first housing parthas a flat first covering portion covering the second electrode, and thesecond housing part has a flat second covering portion covering thefirst covering portion, the first and second covering portions includingthe said openings.
 10. A dispensing device according to claim 2, whereinthe end wall has shroud means defining a cavity in which the electrodeunit is at least partly housed when in its adjustment position, and wallmeans are detachably secured to the shroud means to prevent electrolytefrom the second chamber entering the cavity prior to activation of thedevice.
 11. A dispensing device according to claim 10, wherein the wallmeans is separate from the electrode unit.
 12. A dispensing deviceaccording to claim 10, wherein the wall means comprise part of theelectrode unit.
 13. A dispensing device according to claim 10 whereinthe wall means comprises said second housing part.
 14. A dispensingdevice according to claim 10, comprising activating means actuable todisplace the wall means to enable the first and second electrodes to becontacted by the electrolyte in the second chamber.
 15. A dispensingdevice according to claim 14, wherein the activating means comprisesscrew means rotatable to displace the electrode unit so that the wallmeans is moved out of sealing engagement with walls of the thirdchamber.
 16. A dispensing device according to claim 15, wherein the wallmeans is connected in a snap-fit connection and is disconnected when thescrew means is screwed to exert a force on it.
 17. A dispensing deviceaccording to claim 1, wherein the first and second electrodes areassembled in an electrode unit so as to block a tubular passage openinginto the second chamber, and the adjustment means comprises a plugcarrying a covering member, the plug being insertable into the tubularpassage to plug the latter, to position the covering member so as topartially cover an exposed surface of the second electrode and todispense the electrode into the second chamber.
 18. A dispensing deviceaccording to claim 17, wherein the tubular passage and plug are providedwith mating screw-threads, the plug being screwed into and out of thetubular passage.
 19. A dispensing device according to claim 17 whereinthe second electrode is of elongate, cylindrical form positionedcoaxially with the tubular passage when the electrode unit is fixed inthe tubular passage prior to activation of the device and wherein thecovering member comprises a sleeve which is pushed on to the elongateelectrode as the plug is inserted into the tubular passage.
 20. Adispensing device according to claim 19, wherein a number of plugs areprovided each carrying a differently sized sleeve, the amount of surfacearea of the second electrode remaining exposed being determined byselection of the desired plug/sleeve combination.
 21. A dispensingdevice according to claim 1, wherein the second chamber is divided intoa first sub-chamber containing the electrolyte and a second sub-chamberadjacent the piston device, the first and second sub-chambers beingseparated by a dividing wall which during use enables the passagetherethrough of gas but prevents the passage therethrough of liquidelectrolyte.
 22. A dispensing device according to claim 21, wherein thefirst and second electrodes are mounted in wall means defining a wall ofthe second chamber and the adjustment means are actuable to adjust theposition of at least said second electrode.
 23. A dispensing deviceaccording to claim 1, wherein the adjustment means is actuable toadvance and retract said second electrode by sliding movement to adjustthe amount of the surface area of the second electrode exposed forcontact with the electrolyte.
 24. A dispensing device according to claim1, wherein the adjusting means are actuable both before and afteractivation of the device for adjusting the amount of surface area of thesecond electrode exposed for contact with said electrolyte.
 25. A methodof lubricating a machine bearing comprising attaching to the latter adispensing device having cylinder means, dispensing means movable withinthe cylinder means and separating the cylinder means into a firstchamber containing lubricant and having a discharge outlet and a secondchamber containing an electrolyte and a galvanic element comprising asacrificial first electrode, a single gas-releasing second electrodeelectrically connected to the first electrode, and adjustment meansoperatively connected to said second electrode; the first and secondelectrodes being of different galvanically active materials and which,on activation of the device, are brought into contact with theelectrolyte so as to electrochemically generate gas within, and increasethe pressure within, said second chamber thereby causing the dispensingmeans to move within the cylinder means and discharge the lubricantthrough the discharge outlet, adjusting the adjustment means for aselected amount of surface area of the second electrode to be exposedfor contact with the electrolyte, and activating the dispensing deviceto dispense the lubricant over a prolonged period of time into themachine bearing; whereby the length of said prolonged period of time isdetermined by the selected amount of surface area of the secondelectrode exposed for contact with the electrolyte.
 26. A methodaccording to claim 25, wherein the amount of the surface area of thesecond electrode exposed for contact with the electrolyte is adjustedprior to activation of the dispensing device.
 27. A dispensing deviceaccording to claim 1, wherein:said adjustment means includes a pluralityof apertures of different sizes; whereby a selection of discretegas-release rates is provided.